Application of dyestuff bleaching catalysts in the silver dyestuff bleaching process



United States Patent APPLICATION OF DYESTUFF BLEACHING CATA- LYSTS IN THE SILVER DYESTUFF BLEACHING PROCESS Walter Anderau, Aesch, Basel-Land, and Rudolf Mory,

Dornach, Solothum, Switzerland, assignors to Ciba Limited, Basel, Switzerland, :1 Swiss company No Drawing. Filed Sept. 5, 1963, Ser. No. 306,690

Claims priority, application Switzerland, Sept. 14, 1962, 10,928/ 62 16 Claims. (Cl. 96-53) The silver dyestulf bleaching process for the production of color component images in photographic layers is based on the knowledge that certain organic dyestuffs, especially azo dyestuffs, are bleached out by photographically produced metallic silver, the degree of bleaching being dependent on the amount of silver present. Reduction of the azo groups occurs, which are split and converted into amino groups. In order to initiate this reaction, alkali-metal halides and other substances such as urea, thiosemicarbazide or especially thiourea or derivatives thereof generally must be present in the dyestulf bleaching bath in addition to acids such as hydrochloric acid, sulfuric acid or citric acid, examples of such alkalimetal halides being potassium bromide, potassium chloride and sodium chloride. A common silver dyestulf bleaching bath thus contains 30 to 80 parts of potassium bromide, 20 to 70 parts of thiourea and 35 to 70 parts of 30% sulfuric acid or hydrochloric acid in 1000 parts of Water.

Although a wide choice is possible in respect of the proportions of the substances used, the bleaching time for dif ferent types of azo dyestuffs varies, for example, between 1 minute and 60 minutes. On the other hand, the gradation of the color image depends not only on that of the silver image but also on the bleaching time. If the silver dyestuif bleaching bath is allowed to act on the material for only a short period, the color image shows a flat gradation curve. The gradation curve becomes steeper the longer the dyestuff bleaching bath is allowed to act on the material. It has been observed that some azo dyestuiis are never quite fully bleached by the amount of silver normally present in a layer, the degree of bleaching achieved being at most to a density of 0.1 to 0.2 compared with the original logarithmic density of 1.0 to 2.0.

It has already been observed that certain substances substantially decrease the bleaching time, for example, from 20 minutes to 2 to 4 minutes, when added to the silver dyestufi bleaching bath in very small amounts. Moreover, dyestuffs that cannot be bleached at all or that cannot be fully bleached are completely bleached in the presence of such catalysts. Such catalysts are, for example, dimethyl-quinoxaline, pyridine, picolines, quinolines and aminothiazoles; especially effective are 2-hydroxy-3- aminophenazine and 2:3diaminophenazine The incorporation of a catalyst in the layer during the casting process together with the dyestuff has also been described.

3,318,700 Patented May 9, 1967 The action of the catalysts on difierent types of azo dyestuffs varies considerably. It may be very effective with one kind of azo dyestutf and have virtually no catalytic effect on the bleaching process with another. Thus, there is a need for other catalytically active compounds which, either alone or in admixture with other catalysts, would make possible a uniform rate of bleaching for all three dyestutfs in multilayer material.

This invention is based on the observation that certain naphthazine compounds are specially suitable as dyestuif bleaching catalysts in the silver dyestulf bleaching process.

The present invention provides a process for the production of color photographic images by the silver dyestutt bleaching process wherein there is used an azine compound having at least one acidic group imparting solubility in water and corresponding to the formula in which R represents a naphthalene radical condensed with the azine ring in the manner indicated by the valence lines, which naphthalene radical carries a hydroxyl group, an amino group and/ or an azo group attached to the sixmembered ring not directly bound to the azine ring, and R represents a benzene or naphthalene radical condensed with the azine ring in the manner indicated by the valence lines, as a dyestulf bleaching catalyst.

The compounds of the Formula 3 contain at least one acidic group imparting solubility in water, for example, a sulfonic acid or a carboxylic acid group. Such groups can be bound directly to the carbon atoms which are ring members of the azine compounds, but carboxylic acid groups, in particular, can also be joined to the carbon atoms of the ring systems R and/ or R through a bridge member, for example, through a CH or an --OCH group.

The naphthalene radical R is condensed with the azine ring in such a manner that two adjacent carbon atoms of the naphthalene ring, advantageously in cup-position, are shared with the azine ring. The naphthalene radical R contains a hydroxyl group or an amino group or an azo group attached to the siX-membered ring not directly bound to the azine ring; it can also contain more than one of these groups, for example, a hydroxyl group and an amino group or a hydroxyl group and an azo group. A sulfonic acid group can also be present in this ring. The azo group which is bounud on one side to the naphthalene radical R is bound on the other side, for example, to a benzene radical or to another naphthalene radical.

R can be a benzene radical or a naphthalene radical, which can also correspond to the definition of R thus forming, for example, azine compounds having a centrosymmetric constitution of the kind. exemplified by Formula 6a.

The radicals R and R and more especially the radicals bound to the naphthalene radicals through an azo group can contain further substituents of the kind defined or other substituents, for example, halogen atoms such as chlorine, alkyl groups such as methyl and ethyl groups and alkoxy groups such as methoxy and ethoxy groups.

5 Even larger molecules of azine compounds of the Formula Specially important are the azine compounds containing at least one sulfonic acid group that correspond to the formula R4 H t in which R has the meaning given above and R represents an amino group or an azo group bound to a further aromatic radical. Also worthy of special mention are the azine compounds of the formula (5) SOaH (in which R and R have the meanings given above), and also those of the formula in which R, and R, may be identical or different and represent an amino group or an azo group bound to a further aromatic radical.

Some of the azine compounds to be used in the process of the invention are known; the azine compounds can be prepared by known methods.

In the process of the invention the said catalysts may be added to the dyestuff bleaching bath in a solution containing one gram of catalyst per liter of water in an amount of 1 to 50 cc. per liter of bleaching bath. In a bath that contains for example, 30 parts of potassium bromide, 30 parts of thiourea and 35 parts of 30% hydrochloric acid in 1000 parts of water, a blue azo dyestutf of the formula HOsS- for example, is bleached very slowly, and even after 30 minutes the'layer is not quite colorless at the places where the silver was at maximum density, but if a solution of 1 g./ liter of the catalyst of the formula (8) SOaH 803K 10 H0% $011 is added to such a bleaching bath in an amout of 1 to 4 cc. per liter of bleaching bath, other conditions being the same, the places where the silver was at maximum density are completely colorless after 3 to 6 minutes. Similar results are obtained with the catalysts of the formulae SOaH N OH and H03s- OH H0 sour The catalysts herein described can be used singly, in pairs or in mixtures comprising more than two such catalysts and, if desired or required, they can also be used in admixture with other catalysts, for example, pyridine, aminohydroxyphenazine or quinoxaline. It is also possible to allow the catalysts to act on the material for some minutes in a separate bath prior to the treatment in the bleaching bath. If this procedure be adopted the material can be treated in the subsequent silver dyestutf bleaching bath without a catalyst of the invention or in the presence of other catalysts. Finally, it is also possible to add the catalysts to the emulsion prior to casting, thus incorporating them in the layer along with the silver halide and the dyestuff. By adopting this method, it is possible to incorporate in each dyestutf gelatine layer of three-color material the catalyst most suitable for each individual layer thus making possible a uniform bleaching of all the layers within the same period of time.

SOaH

6 The non-diifusing naphthazine compounds of the folm=an integer of at least 6 lowing formulae are specially suitable for incorporation rr=1 or 2 111 the lers: The compound of the Formula contains a difiusion inhibiting substituent in the radical of the diazo com- 50311 Ho=s- H H0; SOaH H I N SOaH K035 K033 OzN CH=CH -N= I) \l N N SO:1H SOaH HOaS Hots N=N (I11 -N=N HO 1 f t HN o /ONH (15) ponent (I). Compounds also suitable for use as catalysts in the process of the present invention are those of the formulae \N Hots N-N N Boss- BIO: H0 7' IR r O CHIP-CH! /n-l jm H6 HOaS- HaN- (18) SOaH 0.5 mol of 1-aminobenzene-4-sulfonic acid is diazotized in the usual manner, and the diazo suspension is mixed with 0.5 mol of Z-phenylamino-S-hydroxynaphthalene-7- sulfonic acid and 500 cc. of water, while cooling with ice. The pH value of the coupling mixture is then adjusted to 2.5 to 3.0 by the addition of sodium acetate. The mixture is stirred for 3 hours at to 5 C. and then for 16 hours at room temperature. Concentrated hydrochloric acid is then added until the pH value is 0.8 to 1.0 and the mixture is heated for 1 hour at 80 to 90 C. The temperature is allowed to drop to about 50 C., whereupon the mixture is filtered and the filter radical is Washed with 5% hydrochloric acid. The product so obtained of the Formula 16 is then pasted in /2 liter of water, and the pH of the mixture adjusted to 7 by the addition of sodium hydroxide solution and sodium acetate. The mixture is quickly suction-filtered, and the filter radical recrystallized from water. The yield is about 75% of the theoretical yield. The product is a green-yellow powder when dry.

By using in the place of 2-phenylamino-5-hydroxynaphthalene-7-sulfonic acid an equivalent proportion of 2-(4'-methoxyphenyl)-amino-5 hydroxynaphthalene 7- sulfonic acid, 10-methoxy-4-hydroxybenzo[a]-phenazine- Z-sulfonic acid of the formula (J-CH Hots-- I H0 is obtained by the same process. It is a yellow-olive powder.

0.1 mol of 4 hydroxybenzo[aJ-phenazine 2 sulfonic acid of the Formula 16 are introduced into 500 cc. of water. A diazo suspension prepared in the usual manner from 0.1 mol of 1-aminobenzene-4-sulf0nic acid is added thereto. The pH value is adjusted to 9.8 to 10.0 by the subsequent addition of sodium carbonate, and the coupling mixture is stirred for 16 hours at room temperature. The dyestutf is then precipitated with sodium acetate and filtered. It is then dissolved in 1200 cc. of water, the solution is adjusted to pH 7.5 with a small amount of acetic acid, and the dyestuff is again preciptated with sodium acetate. The dyestufi is again isolated by filtration, washed free from acetate with ethyl alcohol and dried in vacuo at C. The yield is about of the theoretical yield. The azine compound of the Formula 18 so obtained is a dark brown powder. The aminoazine compound of the Formula 17 can be obtained from this azine compound containing an azo group by reduction with sodium hydrosulfite.

By coupling diazotized aromatic monamines or tetrazotized diamines with the hydroxyphenazines of the Formulae 8, 16 and 19, further azoazines are obtained that can be used as dyestulf bleaching catalysts. These products are prepared by known methods, for example, by the method used to prepare the substance of the Formula 18 described above.

As examples of products that can be prepared in this manner there may be mentioned those of the Formulae l2 and 13, and those of the following formulae N I l I \N ITTH Hoes- N=N l \N/ HO (Ill-CH SOzH HOaS HaO-O H O S O H SOBH SOaH The following table indicates the color of these substances in a neutral aqueous solution, in an aqueous sodium hydroxide solution and in an a acid solution.

SOrH

I C-NH SOsH HOaS- OH N HOsS- HOaS Yellow-brown Dull orange. Red-violet Red Redbrown. YelloW-brown. Greyblue. Brownish. Grey-blue.

i et.

Bordeaux V 01 l Precipitation.

queous hydrochloric 50 The following examples illustrate the invention, the parts being by weight unless otherwise stated:

Example 1 The following layers are applied successively to a cellulose acetate film provided with an adhesive layer:

(1) A red-sensitized silver bromide emulsion in gelatine that contains the cyan dyestuff of the formula HORS- O-GHr SOrH 1 1 1 2 (2) Gelatine intermediate layer. Example 2 A green-sensitized Silver bromide emulsion in gala A silver bromide gelatine emulsion that contains the time that contains the magenta dyestutf of the formula cyan dyestufi of the formula (26) NH: H038 SOaH NH! t t 6 N=N NH-C-C NHC-HNO-HNON=N OH HO- H038 OaH (4) A yellow filter layer that contains the dyestufl? of 15 (29) the formula (27) SOSH -COHN OH Bio-o no A blue-sensitized silver bromide emulsion in gelain an amount that gives an R-density of 0.75 is applied tine that contains the dyestuff of the formula to a cellulose acetate film provided with an adhesive 1103 s SOzH t O I a H2O SOaH H038 and as precipitating agent a mixture comprising the reaclayer. The film is exposed behind a stepped wedge, then tion product of dicyano-diamidine and formaldehyde, a hardened, developed and fixed in the usual manner. small amount of sodium formate and sodium bi-sulfate. When the image is treated in a bath that contains 100 (6) A gelatine protective layer. parts of potassium bromide, 10 parts of thiourea and 70 This film is exposed four times behind a neutral wedge parts by volume of 37% hydrochloric acid per 1000 parts in the following manner: by volume of bath, even after a -minute treatment only (1) With red light only, traces of the dyestutf are bleached as determined after (2) With green light only, r removing the residual silver in one of the usual silver (3) With blue light only, bleaching baths and then fixing.

(4) With red, green and blue light, When, in accordance with the invention, the developed the exposure being controlled in such a manner that the and fixed image is treated, prior to treatment in the same fourth wedge appears a neutral grey after processing. dyestuff bleaching bath, in one of the baths listed in After hardening in a formaldehyde .bath, the film is de- Table II a color image is obtained which is the reverse of veloped in a Metol-hydroquinone developer and then the original silver image and in which the dyestuff has treated in an acetic acid stop bath and in a fixing hath been completely bleached in the area that originally concontaining thiosulfate. tained the greatest density of silver.

After Washing in Water for about 5 minutes, the film is treated in the following dyestuff bleaching bath:

POFaSSIum bromlde gra'ms' 100 Catalyst, Amount 0! Time of treat- Time of treat- Th1ourea dO 1O formula catalyst, ment in premerit in dyestufl Hydrochloric i (37% Ina/liter g g bath. l g bath,

1.25% solution of the addition product of 35 mols of ethylene oxide and 1 mol of octadecyl alco- 10 10 5 hol cc 10 50 10 5 Azine compound of the Formula 18 milligrams 3 1? g g Bulked with water to cc 1000 18 g The film is then washed with water, the residual silver g8 18 g is re-halogenated in a copper sulfate or copper nitrate 50 10 5 bath made strongly acid with hydrochloric acid, washed 24 5 again, fixed for the second time, washed and then dried.

The time of treatment in the dyestufit bleaching bath should be just suflicient to bring about complete bleach- 7 ing of the dyestufis in all layers at the places most highly E l 3 exposed, the said time of treatment having been determined by tests. It is much shorter than when the opera- A colored gelatin silver bromide layer is prepared by tion is carried out without the phenazine compound in mixing 5 grams of 5% aqueous solution of a cyan dyethe dyestuff bleaching bath. stuff of the formula with 3.3 grams of' a silver bromide gelatine, casting 10 cc. of this mixture on to a glass plate measuring 13 cm. x 18 cm. and then drying it. The layer so prepared is exposed under a master image and the silver image is developed in a developer that contains 6 grams of l-methylamino-4-hydroxybenzene, 6 parts of anhydrous sodium carbonate, 20 parts of sodium borate and 80 parts of crystalline sodium sulfite per liter of Water. After a short rinse, the layer is fixed for to 7 minutes and bleached in a silver dyestuff bleaching bath that contains 30 to 70 cc. of 37% hydrochloric acid, 20 grams of potassium bromide, 20 to 50 grams of thiourea and 4 cc. of an 0.1 aqueous solution of the catalyst of the Formula 8 per liter of water. After bleaching for 8 to 10 minutes at 20 to 22 C., the dyestutf is bleached at the areas containing silver to a degree proportional to the amount of silver present. After removal of the excess silver in a bleach fixing bath, a color image is obtained the dark and light areas of which exhibit the same blue tint. By using instead of the azine compound of the Formula 8, 2-hydroxy-3-aminophenazine of the Formula 1 as catalystor dimcthyl-quinoxaline, the tint of the areas of the image that are only partly bleached is changed to red-violet and the image is therefore unusable. The silver halide layer described herein can form a part of three-color material.

Example 4 A solution of 5 mg. of the dyestufi of the Formula 29, 20 mg. of 2-phenylamino-4:6-dichloro-l:3:5-triazine-4- sulfonic acid and 0.1 mg. of the catalyst of the Formula 12 in 3.5 cc. of water is mixed with 3.3 cc. of 6% gelati-ne solution and 3.3 cc. of silver bromide gelatine. The mixture is cast on a glass plate measuring 13 cm. x 18 cm. provided with an adhesive layer. When the layer is dry it is exposed in the usual manner behind stepped wedges and the silver image developed and fixed in the usual manner.

When a color silver image prepared in the above manner is treated for 5 to 10 minutes in a bleaching bath of the same composition as that given in Example 2, a blue stepped wedge that is bleached pure white at the areas where the original density of silver was greatest was obtained after removal of the residual silver and fixation.

When exactly the same procedure is followed, but with the catalyst omitted, almost no perceptible bleaching of the cyan dyestulf occurs, even after a treatment of to 20 minutes in the bleaching bath.

What is claimed is:

1. A process for the production of a color photographic image by the silver dyestuff bleaching process, which comprises carrying out the bleaching operation in the presence of an azine catalyst that contains at least one acidic group imparting solubility in water and that corresponds to the formula I R: N in which R represents a naphthalene radical condensed with the azine ring in the manner indicated by the valence lines which naphthalene radical contains at least one substituent selected from the groups consisting of a hydroxyl group, an amino group and an azo group, said substituent being attached to the six-membered ring not directly bound to the azine ring, and R represents a member selected from the group consisting of a benzene radical and a naphthalene radical condensed with the azine ring in the manner indicated by the valence lines.

2. A process for the production of a color photographic image by the silver dyestuff bleaching process, which comprises carrying out the bleaching operation in the presence of an azine catalyst that contains at least one sulfonic acid group and that corresponds to the formula in which R represents a member selected from the group consisting of a benzene radical and a naphthalene radical condensed with the azine ring in the manner indicated by the valence lines, and R represents a member selected from the group consisting of an amino group and an azo group bound to a further aromatic radical.

3. A process for the production of a color photographic image by the silver dyestuif bleaching process, which comprises carrying out the bleaching operation in the presence of an azine catalyst of the formula SOaH in which R represents a benzene radical condensed with the azine ring in the manner indicated by the valence lines, and R represents an amino group.

4. A process for the production of a color photographic image by the silver dyestufi bleaching process, which comprises carrying out the bleaching operation in the presence of an azine catalyst of the formula SOsH in which R represents a naphthaline radical condensed with the azine ring in the manner indicated by the valence lines, and R represents an amino group.

5. A process for the production of a color photographic image by the silver dyestuff bleaching: process, which 7 lines, and R represents an azo group bound to a benzene 3,318,700 1 5 1 6 comprises carrying out the bleaching operation in the presence of an azine catalyst of the formula SOaH 10 N l H0 in which R represents a benzene radical condensed with the azine ring in the manner mdlcated by the va ence 10' A process for 16 production of a color p radicaL graphic image by the silver dyestuff bleaching process, 6. A process for the production of a color photographic whlch compnses carry.mg out the bleachmg Operation m image by the Silver dyestufl bleaching process which the presence of the azine catalyst of the formula comprises carrying out the bleaching operation in the presence of the azine catalyst of the formula 20 SIOaH HOaS-N=N- ml HO N N/ HzN 7. A process for the production of a color photographic HO image by the silver dyestufi bleaching process, which comprises carrying out the bleaching operation in the pres- 11. A process for the production of a color photocnce of the azine catalyst of the formula graphic image by the silver dyestuff bleaching process,

N\ N l N -s03H HOHS OH HOaS SOaH H 8. A process for the production of a color photowhich comprises carrying out the bleaching operation in graphic image by the silver dyestuff bleaching process, the presence of the azine catalyst of the formula which comprises carrying out the bleaching operation in the presence of the azine catalyst of the formula N N l N SIOaH nos s Hots Hols at; Ht)

lJTOceSS for Production of a Q P 12. A process for the production of a color photographic image by the silver dyestuff bleaching process, graphic image by the silver dyestulf bleaching process, which comprises carrying out the bleaching operation in which comprises carrying out the bleaching operation in ,the presence of the azine catalyst of the formula V 7 the presence of the azine catalyst of the formula N 5 i N l TH HOaS- NA "N=N 10 L H0 13. A process for the production of a color photographic image by the silver dyestufr' bleaching process, 15 which comprises carrying out the bleaching operation in the presence of the azine catalyst of the formula HaO-O 0-4311;

N l i N SO3H SOaH- N=NQOH=OHON=N OH S0311 1103's H0 14. A process for the production of a color photographic image by the silver dyestutf bleaching process, which comprises carrying out the bleaching operation in the presence of the azine catalyst of the formula O R KI N I I N SOaH HN-(J c-NH Hois- I N=N- Q-N=N H HOsS SOaH OH 15. A process for the production of a color photographic image by the silver dyestufi bleaching process, which comprises carrying out the bleaching operation in the presence of the azine catalyst of the formula HO S0311 H038 OH N N y 1 N N HOaS- H SOsH H018 H0 3,318,700 1. 16 A process for the production of a color photowhich comprises carrying out the bleaching operation in graphic image by the silver dyestulf bleaching process, the presence of the azine catalyst of the formula 110- $0311 HOaS- 0H OH N N N i N SOaH HN([1 i l-NH HOaS- 5H HOaS SIOQH H(|) References Cited by the Examiner UNITED STATES PATENTS 2,410,025 10/1946 Gaspar 96--53 2,627,461 2/ 1953 Friedman 96-53 J. TRAVIS BROWN, Primary Examiner.

NORMAN G. TORCHIN, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N0. 3,318,700 May 9, 1967 Walter Anderau et a1 n the above numbered pat- It is hereby certified that error appears 1 nt should read as ent requiring correction and that the said Letters Pate corrected below.

Column 15, lines 3 to 12, for the right-hand portion of the formula reading "R read R Signed and sealed this 21st day of November 1967.

(SEAL) Attest:

EDWARD J. BRENNER Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer 

1. A PROCESS FOR THE PRODUCTION OF A COLOR PHOTOGRAPHIC IMAGE BY THE SILVER DYESTUFF BLEACHING PROCESS, WHICH COMPRISES CARRYING OUT THE BLEACHING OPERATION IN THE PRESENCE OF AN AZINE CATALYST THAT CONTAINS AT LEAST ONE ACIDIC GROUP IMPARTING SOLUBILITY IN WATER AND THAT CORRESPONDS TO THE FORMULA 